emblance to each other, either by imitation and convention
(language, rites, ceremonies), or from the influence of custom and
obligatory regulations (social institutions, political institutions in
countries where the authorities are obeyed). A large number is requisite
for facts where individual initiative plays a more important part (art,
science, morality), and sometimes, as in respect of private conduct, all
generalisation is as a rule impossible.

VI. Descriptive formulae are in no science the final result of the work.
It still remains to group the facts in such a way as to bring out their
collective import, it still remains to search for their mutual
relations; these are the general conclusions. History, by reason of the
imperfection of its mode of acquiring knowledge, needs, in addition, a
preliminary operation for determining the bearing of the knowledge
acquired.[207]

The work of criticism has supplied us with nothing but a number of
isolated remarks on the value of the knowledge which the documents have
permitted us to acquire. These must be combined. We shall therefore take
a whole group of facts entered under a common heading--a particular
class of facts, a country, a period, an event--and we shall summarise
the results yielded by the criticism of particular facts so as to obtain
a general formula. We shall have to take into consideration: (1) the
extent, (2) the value of our knowledge.

(1) We shall ask ourselves what are the blanks left by the documents. By
working through the scheme used for the grouping of facts it is easy to
discover what are the classes of facts on which we lack information. In
the case of evolution, we notice which links are missing in the chain of
successive modifications; in the case of events, what episodes, what
groups of actors are still unknown to us; what facts enter or disappear
from the field of our knowledge without our being able to trace their
beginning or end. We ought to construct, mentally at any rate, a
tabulated scheme of the points on which we are ignorant, in order to
keep before our minds the distance separating the knowledge we have from
a perfect knowledge.

(2) The value of our knowledge depends on the value of our documents.
Criticism has given us indications on this point in each separate case,
these indications, so far as relating to a given body of facts, must be
summarised under a few heads. Does our knowledge come originally from
direct observation,